The COVID-19 pandemic has now spread from high- and middle-income countries to low-income countries, including Haiti and Tanzania. The natural history of COVID-19 is unknown in low-income countries. We propose to study a combined cohort of 3,054 adults in Haiti and Tanzania to determine the attack rate of SARS-CoV-2 infection and severe COVID-19, to examine interactions with HIV infection, pulmonary tuberculosis, and hypertension in populations of African descent, and to determine long term cardiac complications of COVID-19. Cornell University has collaborated with the Groupe Haitien d?Etude du Sarcome de Kaposi et des Infections Opportunistes (GHESKIO) in Haiti for 38 years and for 15 years with the Mwanza Intervention Trials Unit (MITU) in Tanzania. The proposed emergency supplement leverages these collaborations and four established NIH-supported cohorts, which have already been enrolled, to address NIAID priority areas. The specific aims are: 1.To determine the incidence proportion of SARS-CoV-2 infection and the attack rate and risk factors for severe COVID-19, in well characterized cohorts of 3,054 adults from low-income communities in Haiti and Tanzania. Starting May 1, 2020 we will conduct monthly telephone interviews with the 3,054 participants who are in active follow-up to record symptoms of COVID-19 during the pandemic. Participants will also be encouraged to telephone us if they develop new symptoms. We have cell phone numbers for all cohort participants and have established procedures for telephone communication. We will also review hospital records, perform verbal autopsies, and grade severity of COVID-19. We have banked sera from all participants collected in 2016-2019. In September-November 2020 and again in March-May 2021, we will collect follow-up sera and perform serologic testing for the presence of anti-SARS-CoV-2 IgG antibodies. We will determine the odds for development of severe COVID-19 in participants who had HIV, TB, and hypertension. 2. To determine the cardiac complications of SARS-CoV-2 infection in 1,909 adults with known baseline cardiac function. In 1,909 patients who previously had baseline EKGs and echocardiograms (2016-2019), we will repeat cardiac echo and EKG in 2021 to quantify the odds for development of incident left ventricular systolic dysfunction in those who did and did not become SARS-CoV-2 infected. LV function will be quantified by global longitudinal strain. We will also determine incidence of right ventricular systolic dysfunction, pulmonary hypertension and segmental wall motion abnormalities by echocardiogram, and new Q-waves and other abnormalities on EKG. Defining viral infection rates and natural history in low-income countries will be critical for future prevention interventions. Determining risk for people with HIV, TB, and hypertension will improve their care and prevention. Understanding cardiac sequelae of SARS-CoV-2 will improve care for COVID-19 survivors.